This invention relates to a manhole assembly for a roadway or the like wherein a circular cover is seated within a surrounding frame and is removably hinged thereto to implement the pivotal raising and lowering of the cover.
A known manhole construction of this general type has two coaxial pivot shafts projecting laterally from one side of the cover and journalled within respective housings defined in the frame. The shafts are retained within the housings by individual stopper plates removably affixed to the frame. Such a construction requires the stopper plates as additional components, which must be detached from the frame to enable the removal of the cover.
Another known construction has profiled housings in the frame for receiving the pivot shafts and which prevents the cover from being vertically raised in the event of an internal thrust from below, such as a water surge. The profiled housings are fully open and exposed, however, wherefore dirt and debris can accumulate in them and thus hinder or even block the opening of the cover. Moreover, due to the relatively large circumferential separation between the two pivot shafts, if an off-center opening force is applied to the cover which is not equally distributed between the two shafts, the cover can tilt crosswise and become jammed or wedged. If this occurs from a water surge the cover cannot reclose itself under its own weight, which presents a hazard for automobiles and pedestrians.
A construction is also known wherein the cover has rounded support surfaces, but it is installed from the underside of the frame and thus cannot be easily removed. The configurations of the support housings in the frame are also complex and thus difficult to cast.